1. Field of the Invention
The present invention relates to a directional alignment device or direction setting device. The device includes a frame having a rotatably mounted shaft which supports a first belt pulley whose rotational position defines a direction to be set, a rotary motor on the frame that supports a second belt pulley, and an endless belt that extends around the first and second belt pulleys.
2. Description of the Prior Art
There is a need to be able to bring, for instance, optical instruments into a precise position of alignment, such as to bring a laser beam into a precise position of alignment with a given subject. For example, two such laser units that have well known relative positions are able to provide accurate marking of a position with the aid of their mutually intersecting laser beams.
A first requirement is that the device is able to effect this alignment quickly. A second requirement is that the alignment can be achieved with great precision. A third requirement is that the device can be produced at low cost.
These requirements are not normally compatible with one another.
The concept of the invention is based on the use of a rotary stepping motor. Such motors are available commercially and have an angular stepping increment of about 1°. Rotary stepping motors that have finer resolutions are much more expensive. However, even if it were possible to obtain a rotary stepping motor of desired high resolution, say a resolution of 0.001°, with or without gearing, the time taken to rotate the stepping motor through one half of a revolution would be unacceptably long. However, it is possible in principle to improve the angular resolution of a rotary stepping motor, by coupling the motor to a gear or pulley transmission means. For example, the stepping motor may be fitted with a small belt pulley that is connected to a pulley which is ten times its size, by means of an endless belt, wherein the angular step or increment made by the larger pulley will be correspondingly smaller, e.g. in the order of 0.1° instead of 1°. However, as before mentioned the time taken to achieve the necessary higher angular resolutions is unacceptable.
Accordingly, the object of the invention is to provide a modified version of said device with which alignment or a positional setting can be effected in the correct direction with great precision and within a short space of time.
This object is achieved with the present invention.